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EagleHasLanded writes "The U.S. Metric Association has been advocating for metrication since 1916 – without much success. In the mid-1970s, the U.S. government passed the Metric Conversion Act, but now it seems the time for complete conversion has come and gone. Or could U.S. educators and health & safety advocates put this issue back on Congress' radar screen?"

It would be great if we could get road signs to be switched over to dual units. E.g., congress could pass a law saying that on the interstate system, any time an old sign is replaced with a new one, it has to have dual units.

Although a number of variants of the metric system emerged in the late nineteenth and early twentieth centuries the term is now often used as a synonym for "SI" or the "International System of Units" - the official system of measurement in almost every country in the world.

Every country has traditional units. China, like Europe, uses metric in almost all engineering, building, legislation. You might buy vegetables in a street market in traditional units, though that's fast fading, but in the supermarket all the packages are marked in litres and grams. The road signs are in km. Your weight is in kgs.Your height in cm.

It's an interesting article, but having been to China, people talk distances between locations in km, and the weights in the market are in grams. China is SI, even if China still officially recognizes ancient measures. Have you, in your Chinese travels, ever seen anything that wasn't measured in SI units?

Slashdot. The only site where Wikipedia trumps reality (at least the OP posted it tongue in cheek).

When I worked in construction, I found inches are better than centimeters, because you can specify your tolerances really well. It's really hard to cut a board to a mm precision with a circular handsaw, but no problem to cut it to 1/16 of an inch. Construction workers are really good at converting */2, */8, and */16. They also tend to be good at using pythagorean triples.

Decimal units were actually put into practice first in the US, thanks to Thomas Jefferson who was an ardent proponent of the idea.

He was successful in giving the US had the first decimal currency in the world, and later proposed decimalization of the units of measure.

"to reduce every branch to the same decimal ratio already established for the coin, and thus bring the calculation of the principal affairs of life within the arithmetic of every man who can multiply and divide plain numbers." -Thomas Jefferson

The French picked up the idea when Franklin and Jefferson promoted the idea while in France as ambassadors.

The problem was (like in many things) Congress didn't cotton to a good idea and failed to adopt it when Jefferson proposed it after the adoption of the Constitution.

Jefferson actually advocated the measures be based on the motion of a pendulum at 38 degrees, something that predated the definition of units in the metric system in physical units by almost 200 years.

Note to mods: He's talking about the square socket drive (from, e.g. the ratchet handle), not the size of the socket wrenches themselves.

Just curious, are there any metric drive standards in Europe, and why haven't they found their way to the US?

They're already here because they are the same. They are 6.35mm (1/4"), 9.5mm (3/8"), and 12.7mm (1/2").

There would be absolutely no upside to fragmentation in this standard (the only point of which is interchangeability). If you think the point of the metric system is to have everything in some integer measurement, then you're converting for the wrong reason.

1 mm is roughly 1/32 Inches - so right off the bat there you've got have the accuracy that you asked for.

Furthermore, it is possible to have decimal millimetres, whilst most construction units are given in mm (eg, a kitchen cabinet is generally 600mm wide, light switches are usually 1500mm above the floor) if you need more accuracy (and you generally don't in construction) then you can specify additional accuracy using decimal places... That's the whole point of the metric system, that using decimal places becomes easy. 1 metre = 100 cm, 10 cm = 0.1 m = 100 mm etc...

If you need to put something in the middle of two points that are, say, 105 mm apart, it's pretty straightforward to specify that the distance is 52.5 mmRulers will often have 0.5 mm markings (again, roughly, 1/64 inch) for the first 50 or 100 mm. If your measure doesn't have half mm markings, it's usually accurate enough to interpolate by eye and put the mark on your materials half-way between two mm marks on the measurement device.